This week, a hunk of space rock half the size of a football field will pass historically close to us, between Earth and our communication satellites. Scientists are certain the asteroid, dubbed 2012 DA14, will not hit Earth. If it did, the resulting explosion would equal around 180 Hiroshima atom bombs.

Asteroids have played an immense role in the history of the earth. They may have seeded the earth with organic elements; they wiped out the dinosaurs (which eventually made evolutionary room for humankind); they may even have brought water to the planet.

While nothing is guaranteed, a collision with something like 2012 DA14 isn’t uncommon. Space is like a three-dimensional pool table, with hunks of rock, ice and metal zipping around us all the time. Half a million objects are estimated to inhabit near earth’s orbit alone.

Our generation of humanity is the first to be able to identify an incoming threat in advance.That new capability poses unprecedented and fascinating moral, philosophical, political and practical questions. Scientists can tell us, with increasing degrees of certainty, whether an object will hit the planet tomorrow, or, in 200 years. They can even predict whether it will land in the ocean or hit New York.

But they can’t do much about it – yet. If they were to identify an incoming civilization-ender 200 years out, what do we owe future generations in terms of R and D to save the planet? And what do the nations owe each other if, say, an incoming object is aimed at a a particular nation?

Enter the planetary defenders, a group of astronomers, physicists and aerospace engineers who have since the early 1990s been locating flying space rocks, painstakingly plotting their orbits, and thinking of ingenious schemes to drag them off course or blow them up should they be on a trajectory toward us. Finally, they have been imagining how the fractious family of man might come together with a contingency plan to literally save the planet, like Bruce Willis and Ben Affleck in Hollywood’s Armageddon.

NASA has identified 94% of the huge, potentially civilization-ending asteroids nearby (none of which is on an earth-trajectory for now). But only about 1 percent of the 500,000 Near Earth Objects around the size of 2012 DA14 orbiting near earth’s orbit have been tracked.

The space agency’s global Spaceguard program connects professional and amateur telescopes looking for smaller NEOs. A telescope in Spain picked 2012 DA14 when it was 2.7 million miles away, and reported it to the Minor Planet Center in Cambridge. Later,scientists calculated its trajectory, based on a few plot points of its movement.

Orbit trackers at NASA’s Jet Propulsion Lab have been right on the money so far – often with very little advance notice. One night in October 2008, the Minor Planet center spotted a small object hurtling toward earth. NASA’s scientists plugged the rock’s coordinates into a computer and predicted an impact time and location –20 hours hence, somewhere in the Middle East.

NASA officials called the State Department, concerned that Middle Eastern governments understood that the streaking object they would soon see overhead wasn’t a missile. “For a while, we had it predicted heading toward Mecca,” one NASA official said. “And that was a concern.”

The object landed near a fly-specked train station outpost deep in the Sudanese desert, close to where NASA’s scientists had predicted impact. A few months later, students from Khartoum, following NASA’s map, located the object’s remnants in the sand.

In 2002, Apollo astronaut Russell Schweickart and others founded the B612 Foundation, (named after the asteroid in Antoine St. Exupery’s story The Little Prince). Schweickart became a leading proponent of the foundation’s “audacious project” of saving the earth, after hearing a geologist give a public lecture about how an asteroid impact had once boiled the oceans. A New Jersey farmer’s son with degrees in aeronautics from MIT, and a New Age philosophical bent, Schweickart has been proselytizing about the need for planetary defense ever since.

“I got interested number one, just as a human being, if you can predict a disaster coming and you can prevent it there is a kind of obligation that you ought to do that,” he said.

The B612 Foundation plans to launch a satellite telescope into the orbit of Venus to add another eye in outer space to the Spaceguard program.

In 1995, Congress—thanks in part to Schweickart and other planetary defenders–got NASA to take asteroids seriously. But the global financial situation and the fractious family of man, do not bode well for the larger aims of planetary defense. Designs for ingenious machines and methods to protect the planet – from nuking incoming NEOs to launching giant magnets to drag them off their orbits – are on paper, but have never been tested. (An additional problem: magnets are useless against the overwhelming share of asteroids, which are silicate, not metal.) One of the proposals at the last international conference of Planetary Defenders was a dual spacecraft kinetic impactor to nudge an incoming rock off course. Designed by a young team of physicists and engineers at the European Space Agency, it was called the Don Quixote project. The reference to literature’s most famous windmill-tilter needed no explanation.

This month in Vienna, the Scientific and Technical Subcommittee of the U.N’s Committee on the Peaceful Uses of Outer Space will finalize formal recommendations on international asteroid defense coordination. The recommendations go before the full UN General Assembly this fall.

Schweickart has been pushing for such a plan at the U.N. for years. But he told TIME he doesn’t think most world leaders will pay attention until an actual object is incoming, anyway. “The first time a threat arises is the earliest time that most countries will become aware of this work, despite the fact that their representatives probably were part of the approval process. My personal guess is that many, many issues will be debated that should have been anticipated and simulated well ahead of time. It would not surprise me at all that this debating will continue, until it is too late to act.”